Hi, I am new to Swift, and I have several questions about how ARC works in Swift.
1. I read from one of the previous discussions in the swift-evolution list ( https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160208/009422.html) that ARC operations are currently not atomic as Swift has no memory model and concurrency model. Does it mean that the compiler generates non-atomic instructions for updating reference counts (e.g. using incrementNonAtomic() instead of increment() in RefCount.h)? 2. If not, when does it use non-atomic ARC operations? Is there an optimization pass to recognize local objects? 3. Without the concurrency model in the language, if not using GCD (e.g. all Swift benchmark applications), I assume Swift applications are single-threaded. Then, I think we can safely use non-atomic ARC operations. Am I right? 4. Lastly, is there a way to measure the overhead of ARC (e.g. a compiler flag to disable ARC)? Thanks, Jiho
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